Add music api

[JiepengTan]

1. implement:

• Separate (background) music & sound effect #343

2. test project: (please build your engine from source before run it)

16-BGM.zip

3. scene config:

{
  "bgm":"bgm",
  "zorder": [
    "Bullet"
  ]
}

4. demo script:

onStart => {
	println "onStart"
	wait 1
	play "bgm", {Music:true, Action: PlayPause}
	println "PlayPause"
	wait 1
	play "bgm", {Music:true, Action: PlayResume}
	println "PlayResume"
	wait 1
	play "bgm", {Music:true, Action: PlayStop}
	println "PlayStop"
	wait 3
	play "bgm", {Music:true, Action: PlayRewind}
	println "PlayRewind"
}

5. demo video: please download this video and play it (github can not play audio)

ispx2_music.mp4

[nighca]

Is this a breaking change for existed API Game.Play?

If Game.Play is called with the original way (without specifying field Music), that results in different behavior than spx v1.

[JiepengTan]

Currently, audio only has a play function, (and pause, resume, etc., have been removed). From a typical game development perspective, the need to pause audio is unnecessary. I've developed many games and never needed it.

If you all consistently believe that this SFX needs a pause feature, I'll add it later.

[nighca]

If you all strongly believe that this SFX requires a pause feature

I'm uncertain about the necessity of a pause feature, actually I haven't used that either. But I don't think it's the right time to implement a breaking change to the APIs now.

I will add it later.

No problem.